Fasteners for thin (ish) GRP panels

[Stratos Fear]

I cant remember the name of the fasteners which consist of a loosely held nut in a rectangle of steel with a hole at each end for pop rivetting. I need some for my door cards - can anybody advise me what they are called so I can find them on E-bay ?

As an alternative, I have tried "well nuts" (sounds like slang for an earnest vegan!) which are the compressible rubber things with a brass threaded insert but in my experience they pull out fairly easily.

Any ideas? (and I dont want to use self-tapping screws - sorry!)

Thanks

Peter